How can you test a wheel speed sensor ... resistance etc.

[Submariner1]

I want to test my sensors, one u tube video shows someone testing dc resistance and says 1.6K ohms is about right .. but what value should my CL 500 sensors have?

Sadly I cant just buy one sensor at £119 each, to test each one ... surprisingly they are all different for each wheel.

Another shows one setting a multimeter to AC Volts and connecting to the sensor cable and spinning the wheel and the voltage fluctuates . Any idea what voltage is OK?
Does the voltage increase with the speed of the wheel (as it increases?)
( this looks difficult to test as the wheel doesnt exactly spin fast )

 

[LostKiwi]

What problem are you seeing?

 

[Submariner1]

What problem are you seeing?

Constantly on start up
“ABS and ESP currently unavailable - see owners manual. Says didnt complete auto startup diagnostics .
This clears itself in 15 ft of driving.
MBII says improbable readings from 3 then 4 wheel sensors. Recommended inspect wheel speed sensors .
If battery is low circa < 12.4 or 12.5V then

Four of these pages all the same.

And one new issue , a scary session, where 5 times in a row I got “ESP Inoperative see owners manual”, and “run flat indicator Operative” ( note I has just successfully? reactivated that after doing the tyre pressures, these would not clear themselves by driving, and MBII could not clear them. Just said clear was unsuccessful.
Combined with a funny fault code

Oh and the speedo showed 160mph in the driveway!

Thankfully these “new today” issues have disapeared on the last start up and a 29 mile fast drive. Stayed all good message free.

I have cleaned the front sensors and reluctor rings ,they looked ok ish to me and are now clean (well the reluctor rings look like ground steel with a shiny groove in the centre that looks segmented).

I will clean the rear sensors and rings tomorrow.

Just want to fire her up and see a clean display and drive it!
Done all the tarting up and bringing her up to spec to be rewarded by this

I still half suspect low voltage seems to kick this off.

 

[LostKiwi]

The clue here is "see owners manual" not "visit workshop"...

 

[Submariner1]

The clue here is "see owners manual" not "visit workshop"...

Sorry I dont understand. The manual says to drive it and turn wheel left and right.

Yes, this action clears the message and I can understand, that a fix like this for very infrequent issues is fine.
But, are you saying one should just ignore this dash display message even if it happens EVERY single time you start the car? Surely thats unacceptable.

Well I have never had a Mercedes, that had dash messages except once in a blue moon.

 

[LostKiwi]

What it means is you're looking in the wrong place.
If it was a mechanical/electrical issue with a sensor it would be 'visit workshop'sbut the message is to 'see owners manual'
One implies a problem which is user rectifiable and the other implies not user rectifiable ergo this is not an issue with wheel sensors as users cannot rectify a failed wheel sensor.

The cause of why the car is losing the steering angle position is what you need to be looking for. You already suspect the battery so that's s good place to start, not wheel sensors.

 

[Submariner1]

What it means is you're looking in the wrong place.
If it was a mechanical/electrical issue with a sensor it would be 'visit workshop'sbut the message is to 'see owners manual'
One implies a problem which is user rectifiable and the other implies not user rectifiable ergo this is not an issue with wheel sensors as users cannot rectify a failed wheel sensor.

The cause of why the car is losing the steering angle position is what you need to be looking for. You already suspect the battery so that's s good place to start, not wheel sensors.

Thanks Alistair
I suspected that was the difference in terminology but was not sure.
I was on that track until I got the “EPS inoperative” which said visit workshop. But thankfully that was just a quick sucession of 5 events that could not be cleared down ( so would remain) and it thankfully went away and has not returned ... atm I am putting that down to a glitch, and concentrating on the battery.

 

[om613]

BTW, I mentioned 'bad earths' in the your other post, because you've had 2+ bad MB batteries of late.

I had a few issues that I thought pointed towards an 'end of life' battery scenario, last year.
The bullet was thus bitten.

105 Ah. £65 delivered from a top ebay battery seller.